The role of contextual conditioning in the effect of reinforcer devaluation on instrumental performance by rats

Different groups of rats received different amounts of training to lever press for a food reinforcer before an aversion was conditioned to the food. This devaluation of the reinforcer reduced responding in both subsequent extinction and reinforced tests of responding to a degree that was independent of the amount of instrumental training. Moreover, interpolating context extinction between aversion conditioning and the extinction test reduced the magnitude of the devaluation effect, thereby indicating that Pavlovian contextual conditioning may play a role in the instrumental devaluation effect.     

The synthesis, characterization, and alkylation of nacnac chromium triflate derivatives

A Cr(III) triflate coordinated by the bulky β-diketiminate ^MeL^iPr (^MeL^iPr = 2,4-pentane N,N′-bis(2,6-diisopropylphenyl)diketiminate) was synthesized from the corresponding bridging iodide complex [^MeL^iPrCr(μ-I)]₂ by ligand substitution and subsequent oxidation with silver triflate (AgOTf). ^MeL^iPr Cr^III(OTf)₂ exhibits rare trigonal bipyramidal geometry about Cr(III). Attempts to alkylate this triflate synthon with 1,4-dilithiobutane (Li(CH₂)₄Li) led to reduction, while reaction with dimethylzinc (ZnMe₂) led to a mono-alkylated product; only the reaction with methyl lithium (MeLi) was successful in generating a dialkyl.     

Effect of lithium on the melatonin production in the pineal gland of viscacha

Melatonin is synthesized primarily in the pineal gland. Lithium affects the circadian rhythms that may explain its therapeutic effectiveness in the treatment of bipolar disorder. The objective of this study was to investigate the effect of lithium on the biochemical parameters involved in melatonin synthesis in the pineal gland of viscacha. Viscachas were daily intraperitoneally injected with lithium chloride or saline solution for one month. Pineal mRNAs encoding β₁-adrenoceptor and arylalkylamine-N-acetyltransferase enzyme (AA-NAT) were studied by in situ hybridization. Pineal melatonin concentrations were determined by radioimmunoassay, and AA-NAT and hydroxyindol-O-methyltransferase (HIOMT) activities were investigated by radiometric assays. The only parameters that decreased significantly were the expression of AA-NAT mRNA and pineal melatonin levels. Our data suggest that lithium treatment may decrease melatonin synthesis in the viscacha pineal gland by a complex mechanism that involves currently unknown events that are beyond a decrease in the expression of AA-NAT enzyme.     

Differential sensitivity of fungi to lithium chloride in culture media

Forty species of fungi, representing a range of ecological and taxonomic groups, were tested for their ability to grow on agar media amended with lithium chloride (LiCl) at 1.5, 3 and 6 g l⁻¹. Species of Trichoderma varied considerably in their sensitivity to LiCl; at one week on 6 g l⁻¹ LiCl medium, the growth of seven species of Trichoderma was considerably inhibited; however, by three weeks at this level, four of the species tested were able to attain ≥30 % of control growth. Of the seven species tested, an isolate of T. viride was the most sensitive to LiCl in agar. Eleven other imperfect fungi also showed a range of ability to grow on agar amended with LiCl, from total inhibition to complete lack of inhibition. Six ascomycete fungi were greatly inhibited by LiCl at all levels; however, an isolate of Chaetomium globosum was highly tolerant of LiCl. Seven basidiomycete wood-decay fungi were quite sensitive to LiCl in agar, showing total to nearly total inhibition even at the lowest level; however, after three weeks, an isolate of Postia placenta was nearly uninhibited except at 6 g l⁻¹. Five ectomycorrhizal basidiomycete fungi were totally inhibited by all levels of LiCl; however, one ectomycorrhizal imperfect fungus (Cenococcum graniforme) was able to grow at 3 g l⁻¹ and was uninhibited at 1.5 g l⁻¹. Four zygomycete fungus isolates were nearly unaffected in their growth by all levels of LiCl.     

Inhibition of Wnt and PI3K Signaling Modulates GSK-3β Activity and Induces Morphological Changes in Cortical Neurons: Role of Tau Phosphorylation

Glycogen synthase kinase GSK-3β has been identified as one of the major candidates mediating tau hyperphosphorylation at the same sites as those present in tau protein in brain from Alzheimer′s disease (AD) patients. However, the signal transduction pathways involved in the abnormal activation of GSK-3β, have not been completely elucidated. GSK-3β activity is repressed by the canonical Wnt signaling pathway, but it is also modulated through the PI3K/Akt route. Recent studies have suggested that Wnt signaling might be involved in the pathophysiology of AD. On the other hand, modulators of the PI3K pathway might be reduced during aging leading to a sustained activation of GSK-3β, which in turn would increase the risk of tau hyperphosphorylation. The role of Wnt and PI3K signaling inhibition on the extent of tau phosphorylation and neuronal morphology has not been completely elucidated. Thus, in the present investigation we analyzed the effects of different negative modulators of the Wnt and the PI3K pathways on GSK-3β activation and phosphorylation of tau at the PHF-1 epitope in cortical cultured neurons and hippocampal slices from adult rat brain. Changes in the microtubule network were also studied. We found that a variety of Wnt and PI3K inhibitors, significantly increased tau phosphorylation at the PHF-1 site, induced the disarrangement of the microtubule network and the accumulation of tau within cell bodies. These changes correlated with alterations in neuronal morphology. Special issue article in honor of Dr. Ricardo Tapia.     

Effect of Lithium and of Other Drugs Used in the Treatment of Manic Illness on the Cation-Transporting Properties of Na+, K+-ATPase in Mouse Brain Synaptosomes

We have developed and used a novel technique to investigate the effects of lithium and other psychotropic drugs on the cation-transporting properties of the sodium- and potassium-activated ATPase enzyme (Na+,K+-ATPase) in intact synaptosomes. Rubidium-86 uptake into intact synaptosomes is an active process and is inhibited by approximately 75% in the presence of the Na+,K+-ATPase inhibitor acetylstrophanthidin. In vitro addition of lithium to synaptosomes prepared from untreated mice causes a progressive inhibition of acetylstrophanthidin-sensitive 86Rb uptake, but only at concentrations higher than the clinical therapeutic range. However, pretreatment of mice for 14 days in vivo with lithium, carbamazepine, and haloperidol, but not phenytoin, causes a significant stimulation of 86Rb uptake into synaptosomes via Na+,K+-ATPase.     

Assisting effects of lithium on hypoglycemic treatment in patients with diabetes

In this article, we report the assisting effect of lithium on hypoglycemic treatment in patients with diabetes. Thirty-eight diabetic patients, 15 male and 23 female, aged 20–70 yr, 33 noninsulin-dependent diabetesmellitus (NIDDM) patients, and 5 insulin-dependent diabetesmellitus (IDDM) patients, were recruited in this study. Fasting and 1-h postprandial blood glucose (BG) profiles were undertaken from three groups of patients with diabetes before and after short-term of treatment of lithium carbonate. Group I was treated with diet only, Group II with oral hypoglycemic agents (OHA), and Group III with insulin. The fasting blood glucose (FBG) level and 1-h postprandial blood glucose (1-h PBG) level before and after treatment of lithium were: Group I: FBG: 7.67 ± 0.48 vs 7.13 ± 0.82; 1-h PBG 15.13 ± 0.88 vs 10.33 ± 0.96; Group II: FBG: 8.84 ± 0.67 vs 6.04 ± 0.57; 1-h PBG: 12.33 ± 0.72 vs 9.95 ± 0.82; Group III: FBG: 10.87 ± 0.83 vs 6.83 ± 0.79; 1-h PBG: 12.45 ± 0.93 vs 9.17 ± 1.00 mmol/L, respectively. The FBG and PBG of all three groups decreased significantly after lithium treatment, except the FBG in Group I. These data suggest that combined with other therapy, lithium could improve glucose metabolism in most patients with diabetes. Our results suggest that lithium has an assisting hypoglycemic effect on antidiabetic treatment.     

Chitosan-LiOH-urea aqueous solution—a novel water-based system for chitosan processing

A solution of partially N-deacetylated chitosan in aqueous lithium hydroxide (LiOH)/urea was prepared successfully through a freeze-thawing process and the dissolution behavior was studied. The results indicated that chitosan can directly dissolve in LiOH/urea aqueous solution. LiOH mainly contributed to the breakage of intramolecular and intermolecular hydrogen bonds in chitosan. Urea, LiOH, and chitosan formed inclusion compound (IC) with urea as the IC host, and the LiOH-chitosan complex as the guest. Aqueous 4.8 wt % LiOH/8.0 wt % urea was verified to be the optimal solvent for chitosan. The results of rheology and viscosity characterizations revealed that chitosan/4.8 wt % LiOH/8.0 wt % urea aqueous solution was pseudoplastic fluid, and was more stable than the solution of chitosan in acetic acid at ambient temperature.